Irish Weather Statistics

Winter 1739-40 is the second coldest on record within the CET series that goes back to 1659, behind only the Lorna Doone Winter of 1683-84 and slightly ahead of 1962-63.

Monthly CETs for 1739-40

Season|December|January|February|Winter
1739-40|3.2|-2.8|-1.6|-0.40


Data comes from the UK Met Office.

December 1739 as you can see here wasn't an exceptionally cold month really but January and February 1740 certainly were (200 years later, we would achieve a very cold January again in 1940 which up to that point was the coldest month of the 20th century but that's a month for another day).

1740 of course was the year of the infamous Great Irish Frost as well as the forgotten Irish Famine. Previously to 1740, we had a run of relatively mild winters so this season was a huge surprise out of nowhere for people in the UK and Ireland, also Europe.

It is estimated that between 20-38% of the Irish population in 1740 (2.4 million) were killed due to the famine that had occurred. This is around 300,000 to 480,000 deaths. The famine was caused by the extreme cold and the very wet weather that succeeded it. As a consequence of the weather, there were poor grain harvests, a shortage of milk and frost damage to potatoes. Ireland was the most severely affected by the famine in terms of mortality due to the grain and potato failure but the terrible effects from the weather were spread out across Europe.

According to the Irish Independent on March 4th, 2018:

The Dublin Evening Post reported an open-air ball held on the surface of the Boyne, where grandees participated in "several country dances on the ice, being attended by a large band of music".

The party mood didn't last as the cold snap outstayed its welcome. With the ports frozen, the coal supply to east coast households dried up. When the ice eased and imports resumed, coal prices spiked putting it beyond many. This sparked an orgy of illegal tree felling, with 14 arrested for chopping in the Phoenix Park alone. The coal merchants were accused of stockpiling and profiteering.

A series of failed grain harvests in the 1720s had pushed the poor into an ever deeper dependence on potatoes, which by 1740 had become the dietary mainstay of much of the populace. Before the Great Frost had even lifted, noting that the potatoes were frozen in the ground and in storage, Cork estate agent Richard Purcell chillingly predicted: "The eating potatoes are all destroyed, which many think will be followed by a famine among the poor, and if the small ones, which are not bigger than small peas and which be deepest in the ground, are so destroyed as not to serve for seed, I think this frost the most dreadful calamity that ever befell this poor kingdom."

By the end of February the frost had finally vanished, only for the weather to confound and dismay with another cruel twist. The big freeze continued, but it was a bone-dry freeze. As spring turned to summer, temperatures struggled upwards, but there was little respite from the drought, which was felt over a large part of Europe.

The failure of the potato crop caused a big jump in demand for grain, but the drought severely damaged the grain harvest so that wheat, oat and barley prices skyrocketed. For the ordinary person, the soaring grain prices could be directly measured in the shrinking size of the loaf of daily bread. As they had often done before in desperate times, the poor took to eating nettles as a proven source of nourishment. In Dublin, Drogheda and other towns, there were food riots and the looting of shops and storage depots.

The weather played more cruel tricks as Christmas 1740 neared. Blizzards in October and November were followed by torrential rain in December which in turn was followed by a sudden deep freeze. Billions of tons of water locked up as ice were suddenly liberated by a sharp warming which caused flash floods, propelling deadly miniature icebergs into the paths of boats and buildings.

The catastrophe came to a horrible head in the spring and summer of 1741, dubbed Bliain an Áir, or the Year of Slaughter. Starvation compounded a range of diseases and led to epidemics of 'flux' (dysentery), typhus and other ills.

1740 was likely caused by the eruption of Mount Tarumae, Japan in August 1739 (which had a volcanic explosivity index (VEI) of 5, very high) and volcanic eruptions on the Kamchatka peninsula in Russia. However, it remains a mystery what led to this extreme event.

A great book that is worth a read is Arctic Ireland: The Extraordinary Story of the Great Frost and Forgotten Famine of 1740-41 by Trinity College History professor, Dr. David Dickson. https://www.amazon.com/Arctic-Ireland-Extraordinary-Forgotten-1740-41/dp/1870132858

There are reports of temperatures in Ireland being well below our current record of -19.1c at Markree on January 16th 1881 with suggestions of near -30c. I think it's more realistic to say that lowest temperatures could have been around -20 to -22c considering our maritime climate. Like the thoughts of -30c is just a bit too far out there and insane.

What makes 1740 even more remarkable than it already is from what you know here so far is that the 1730s was the warmest decade on record at the time in the CET, De Bilt (Holland) and Uppsala (Sweden) long term temperature series until being beaten over 260 years later in the 1990s. The mildness of the decade is confirmed by the early ice break-up dates for Lake Malaren and Tallinn Harbour. The rapid warming in the CET record from the 1690s to the 1730s and then the extreme cold year of 1740 are examples of the magnitude of natural changes which can potentially be recorded in long series. Consideration of variability in these records from the early 19th century, therefore, may underestimate the range that is possible.

https://www.researchgate.net/publication/226043410_Unusual_Climate_in_Northwest_Europe_During_the_Period_1730_to_1745_Based_on_Instrumental_and_Documentary_Data

Very in-depth paper on 1740-41.

https://www.clim-past.net/9/1161/2013/cp-9-1161-2013.pdf

It's suggested that the extreme cold was down to a very persistent Scandinavian High.

From 'The Little Ice Age' by Brian Fagan (a book suggested to me by Ckit1):

In late 1739, the NAO swung abruptly to a low mode. Blocking anticyclones shifted the depression track away from its decade-long path. Southeasterly air flows replaced prevailing southwesterlies. The semipermanent high-pressure region near the North Pole expanded southward. Easterly air masses from the continental Arctic extended westward from Russia, bringing winter temperatures that hovered near or below zero. Europe shivered under strong easterly winds and bitter cold for weeks on end.

For the first time, relatively accurate temperature records tell us just how cold it was. An extended period of below average temperatures began in August 1739 and continued unabated until September of the following year. January and February 1740 were 6.2C and 5.2C colder than normal (!). Spring 1740 was dry with late frosts, the following summer cool and dry. A frosty and very wet autumn led into another early winter. In 1741 the spring was again cold and dry, followed by a prolonged summer drought. The winter of 1741/42 was nearly as cold as that of two years earlier. In 1742, milder conditions finally returned, probably with another NAO switch. The annual mean temperature of the early 1740s in central England was 6.8C, the lowest for the entire period from 1659 to 1973

Some extracts on the season.

Harrod's "Antiquities of Stamford"

In the hard frost of 1740, at two different days, a sheep and a hog were roasted on the river Welland, where the ford is at the opening in Water Street. The printers also came and got much money by printing person's names who assembled there. The hard frost began Christmas Eve and lasted til Lady Day 1740; the greatest degrees of cold was on January 5th in the morning; it frequently relented in the forenoon but was sure to return at night; however it was not so intense as the frost of 1709, when the Adriatic sea was so frozen that it might be passed on foot, so that the Venetians been at war with the Turks their city might have been taken by a land army..

Dr Huxham of Plymouth

December The weather in this month was altogether surprising; in the beginning we had a northeast wind and a severe frost, presently a rainy and turbulent south wind; in a very short time after a southwesterly and a great deal of rain, the barometer nevertheless rising. The 14th and 15th, the wind was northwest; the 16th, northeast and a return of the frost; the 19th and 20th, a violent southeast; on the 21st again, a stormy southwest; from that of an easterly, a cold northeast wind intervening, the 25th and 27th then a most severe storm from the east, with an exceeding severe frost and a constant exceedingly small snow to the very end. In an instant, a most piercing cold froze up everything, both within doors and without, nay, the very strongest kinds of wines were frozen; indeed whatever was exposed to the air instantly turned to ice. . People even shivered by the largest firesides nor could keep themselves warm in their very beds. January The severity of the cold still continued, such indeed, as was never known in this country. Although the first day of the month, there was a great thaw and a fall of rain, nevertheless the northeasterly wind and a most sharp frost instantly returned which lasted til the very end of the month and although the heat of the sun; all things thawed by day, yet by night were bound by a most rigid frost. The coldest days were the 11th, 15th, 16th, 17th , 18th, 26th, 27th, 28th; nay so severe was the frost which now prevailed that all kinds of wine being exposed out of doors which immediately turned to ice , nay, the very saltwater upon the shores was so, a thing this which very seldom happens in these parts. Innumerable trees and shrubs were cut off by the cold and even the very hardy furzes themselves. A vast number of seabirds flew hither and numbers from foreign countries , which had never been seen here before.

George Smith of Richmond (Surrey), a proctor to Queen Anne

Thames froze over in 4 days, storm of wind 48 hours (30th Dec) Some people walked over the Thames (1st Jan) Frost continued till February 1st, when a thaw began in day, frost returning each night. Ice all gone in Thames upward but not broke about London (Feb 11th) Ice beings to run in Thames (13th Feb) Ice broke in Thames (17th) Ice gone at London (23rd) This was the severest frost I ever known and the most kindly thaw. No rain, roads good, all garden stuff destroyed. Hard frost again in March. A very backward spring, dry and dusty as summer, no considerable rain for 3 months past; the river a slow as ever known. (31st Mar) Very great storm of snow and wind from 10 to 2 (21st Apr) A very cold unkind season (30th Apr) Extraordinarily dry dusty and cold, very unpleasant season (31st May) The coldest weather ever known at Michaelmas, piercing cold (30th Sep) A very unkind year, no good fruit, nor warm weather ; winter severe; storms and frost with great snow."

What an unprecedented and extraordinary piece of history right here, just as much as Winter 1683-84!

British newspaper articles on the cold snap.

1st February 1956









2nd February 1956

echat wrote: »

How do you mean due to GDPR - that only affects personal data?

See for yourself, this shutdown of the site occurred exactly when GDPR came into effect.

Unfortunately, we have had to temporarily shutdown the ECA&D website for security reasons. As soon as these issues have been resolved, the website will become available again. Apologies for the inconvenience.

https://www.ecad.eu/

As an introduction, I'd like to personally say that Spring 2012 was as crazy as 2018. It had a very warm March with unseasonably warm conditions towards the end of the month resulting in the warmest March conditions in Ireland since 1965. I did a post on this warm spell previously in the link aside: https://www.boards.ie/vbulletin/showpost.php?p=106615732&postcount=351

Immediately a week after it, it turned much colder with temperatures under 10c and they remained so for a lot of April in the east of Ireland with the maximum getting up to 13c all month at Casement Aerodrome, its lowest on record for April. This was combined with heavy rainfall with it being the wettest April since 1998 in the east of Ireland whilst some north and west parts were actually drier than average. It was the coolest April since 1989, following the warmest April on record in 2011. The first three weeks of May continued colder than average with frost recorded as late as May 16th. The minimum got down to -3.8c at Thomastown on May 6th, the lowest May temperature in Ireland since 1997 and Dublin Airport got down to -3.0c on the same day which was its lowest temperature for May on record (going back to 1941). At that time, it was looking increasingly like the March warm spell was our Summer in 2012 BUT the weather gods weren't finished with us yet before the dire Summer season itself of 2012 as late May 2012 brought a significant warm spell resulting in the warmest May conditions in Ireland since 1997 (strangely enough the last time a temperature as low as -3.8c was recorded in May also).

The last rain before the dry and warm spell took off, happened on the 18th May 2012 to the south of Ireland with up to 17mm at Coomclogh, Co. Cork with temperatures in the low teens and moderate northeasterly winds - not a pleasant day for mid-May. Into the 19th, this low weakened as pressure began to rise but it was a slow process as there was a lot of cloud over the country with temperatures gradually rising.



By the 21st, the Siberian High had pushed towards Scandinavia and it attempted to link up with the Azores High down to the southwest of Ireland to form one big ridge and turn the winds into a warm easterly. On the 21st, temperatures were up to 21.2c at Glenties, Co. Donegal in skies brightening up as days go by.



Now, see this chart from the 23rd May 2012, that is a classic chart for warmth with a big Scandi high and the easterlies bringing in continental air. It continued to ridge into Ireland on the 24th resulting in widespread sunny skies including up to 15 hours of sunshine at Dublin Airport on this day. Maxima got up to 25.5c at Cavan (Drumconnick) on the 24th.





On the 25th, the easterlies began to strengthen with a fair ol' breeze to the south of the high in across the east of Ireland, England and Wales. Meanwhile, the west of Ireland and Scotland were in the shelter of the wind and enjoyed a hot day for May. Temperatures got up to 28.3c at Ardfert, Co. Kerry on this day, the highest May temperature in Ireland since 1997 and the second highest on record. Shannon Airport reached 27.8c on the 25th, its highest on record for May beating 27.2c in 1997. Inverailort in the highlands of Scotland on this day reached 30.9c, Scotland's highest temperature for May on record (as a reminder, Scotland bet its March record too in March 2012).



The warm easterlies continued for a few days but the warmth did not surpass that of the 25th.



By the 30th, majority of the warmth was gone with showers taking place and the high retrogressed to Greenland which was not a good sign for Summer!



This spell reached some remarkable temperatures indeed. Unfortunately, due to it being an easterly, Dublin did not get the best end of the stick with temperatures generally between 18-21c for the period here. Here's some other temperature recordings during the spell:

Station|Maximum temperature|Date
Ardfert|26.4|26 May
Belmullet|26.1|25 May
Belmullet|25.8|26 May
Belmullet|25.8|27 May
Belmullet|23.4|28 May
Claremorris|23.1|24 May
Claremorris|25.6|25 May
Claremorris|24.0|26 May
Claremorris|24.8|27 May
Glenties|25.2|24 May
Glenties|27.8|25 May
Glenties|25.8|26 May
Glenties|27.4|27 May
Glenties|26.8|28 May
Shannon Airport|25.1|24 May
Shannon Airport|25.7|26 May
Shannon Airport|24.3|27 May
Valentia Observatory|25.9|25 May
Valentia Observatory|24.9|26 May


So, going by the above, Glenties had an official heatwave (minimum 5 consecutive days with a maximum temperature of at least 25c) in May 2012!

Incredible spell or what?

All data come from Met Éireann and the UK Met Office.

Following on from the coldest Winter since 1962-63 and the coldest Spring since 1962, Summer 1979 wasn't anything to write home about. It was cool, wet and dull but not exceptionally so, therefore a very forgettable Summer in the sense of the overall statistics. However, this season stands out for one single event that occurred in mid-August 1979. This was of course the Fastnet Storm.

From a synoptic stand point, what happened was that a depression of approximately 1010mb at this time near Newfoundland in Canada moved eastwards over the North Atlantic Ocean on the 11th/12th August. Rather than the low filling and weakening, it did the opposite with it intensifying as it got closer to Ireland. The low pushed into the southwest of Ireland on the night of the 13th being directed northeastwards over the country. At midnight on the 14th, minimum pressure dropped to 984mb in contrast to the pressure being 1010mb at 16:00 on the 13th. This was a 26mb drop in pressure in an 8-hour period and it was officially a "weather bomb" or in scientific terms, explosive cyclogenesis. What defines a weather bomb is that the pressure of a low drops at least 21mb within a 24-hour period and in this case, the pressure dropped 26mb from 1010 to 984mb within 8 hours! Many of the storms or weather bombs you know of in recent times like say the 9/10 December 2014 or 23 December 2013 have their pressure dropping gradually over the 24-hour period but in August 1979, the pressure dropped very rapidly which led to high seas and unseasonably windy conditions.

From Met Éireann:

Our stations near the south coast (Valentia Observatory, Roche's Point, Cork Airport and Rosslare) all reported winds of near gale or gale force (force 7 or force 8 respectively) with gusts in the range 46 to 52 knots (1 knot = 1.15 mph = 0.515 m/s). However, the maps show the strongest winds just off the south coast where yachtsmen were reporting storm or violent storm force winds with even a suggestion of hurricane force winds (force 12). The winds recorded at the land stations would suggest winds at sea just about reaching storm force 10 but force 11 or force 12! Well the supplementary sources of information, the Fastnet lighthouse, the naval vessel Deirdre and the Marathon Gas Platform, indicate that the yachtsmen did not exaggerate.

Forecast guidance did not convey either the severity of the conditions or the speed with which they developed but then such explosive deepening is very difficult to forecast. However, predictive ability has improved considerably since 1979 and so we may hope that warnings will be more timely and accurate in future.

The maximum wave height recorded at The Marathon Gas Platform was 14.5 metres. In comparison, Storm Darwin of 12 February 2014 caused a maximum wave height of 25m at the Kinsale Energy Gas Platform. August 1979's wave height may not seem that extreme here compared to Darwin but you got to remember that a race was taking place and not to mention, this was in the Summer season.

Look how the low evolves.







Satellite for near midday on 14th August 1979.



Hundreds of yachts were lost and unfortunately, there were 15 fatalities courtesy of the storm.

Was it unprecedented? No. Summer storms like it have happened before and have happened since. They are rare due to the weak zonal flow in Summer time. Two other examples of Summer storms include the one in July 1956 and in July 1988.

http://news.bbc.co.uk/onthisday/hi/dates/stories/august/14/newsid_3886000/3886877.stm

Data come from Met Éireann.

I'm hoping to have some sort of thunderstorm history post today, no guarantee. If I won't have it done, I'll do Summer 1955 which included Ireland's sunniest month on record, July 1955.

For the moment, the daily CET for June 1st was provisionally +5.9c above the average compared to -8.1c below the average on March 1st. #2018 #crazy #year

Ok so this post is going to be looking at the general history of Ireland's thunderstorms, the ones that really stand out, with some stats to back up the summaries. I will likely do detailed posts on some of them in future if possible.

To start off, let's briefly discuss how thunderstorms occur and what they are exactly.

Thunderstorms are very basically storms or heavy rain showers with the combination of lightning and thunder. They occur in the unstable atmospheric conditions favourable for the development of heavy showers but their unique and spectacular features are thunder and lightning. Lightning is an enormous electrical spark caused by the discharge of static electricity either from one cloud to another within a cloud or between a cloud and the ground. The lightning strike causes a sudden and intense heating of the air along its path which in turn causes an explosive expansion producing the loud noise known as thunder. Because a lightning strike can be up to 2km long, the sound from different parts of the flash reaches you at slightly different times which, together with echoes, accounts for the rumbling sounds of thunder that we're familiar with. While the light from the flash reaches you almost instantaneously (since the speed of light is extremely fast at 299,792,458 m/s), the sound from the thunder travels through the air much more slowly at 1km every 3 seconds. Thunder can often be heard up to 15km away. The amount of energy involved in a thunderstorm is enormous. The potential difference just before a lightning strike occurs is estimated at between 100 million and 1000 million volts, and during its most active phase, a thunderstorm will produce about one strike every 20 seconds. A small thunderstorm of about 1km radius is equivalent in terms of energy to ten nuclear bombs of the type that dropped on Hiroshima.

2013 - Following two weeks of very warm to hot weather courtesy of a stubborn area of high pressure with the jet stream well to the north, low pressure approached from the Atlantic on the 22nd into the 23rd July. This came into the warm air already entrenched over Ireland and as the low pushed in, it forced the winds to a southerly direction dragging up some extremely humid and unstable air with nightime temperatures not getting below 15c widely and even 20c in England on the 23rd July in particular. The month went out with a bang as a result bringing thundery downpours to many and high daily rainfalls leading to a wet July for some regardless of the drought that occurred for much of the month. On the evening of the 24th July, heavy thundery showers moved into Leinster and Munster. These brought lightning and heavy rainfall including a daily fall of 62.5mm at Ballincurrig, Co. Cork. This same station had only 2.5mm of rainfall from the 1st to the 20th July. Further thunderstorms occurred days afterwards in continuous high humidity conditions with a daily rainfall of 35.0mm at Merrion Square, Co. Dublin on the 26th.

Could only find one good video of the thunderstorm in Cork (since I know you Corkians would love to see Cork under a thunderstorm). The second two are Dublin.







2012 - June 2012 was a very wet month with a lot of rainfall and for some, the wettest June on record. It was also quite a cool month with daytime temperatures being well below average for much of the month stuck in the 13-16c range. However, near the end of the month, a warm front pushed northwards on the 26th introducing some much warmer air all the way from Spain. Temperatures peaked at 24.8c in Dún Laoghaire, Co. Dublin on the 27th which whilst not a remarkable temperature felt very warm because we had not seen such temperatures since the end of May at that point, mixed with the humid nature of the southerly winds. The warm front brought light rain northwards whilst another band of rain pushed into the south on the night of the 26th into the 27th. This rain was more intense than the previous band but worse was yet to come. On the night of the 27th into the 28th, very heavy thundery rain associated with an active cold front moved northwards over the country with further thunderstorms behind it on the 28th and yes, another band of rain pushed into the south during the evening. In all this time, there was plenty of flash flooding and thunderstorms contrasting with the warm, humid air. Accumulations of 50mm or more were recorded between 21:00 on the 27th and 03:00 on the 28th with Cork being particularly affected. At Cork Airport, 36.1mm of rainfall fell within 3 hours and this sort of event has a return period of 20-30 years showing you how extreme it was. Cork newspapers reported that more than 50 homes and numerous businesses were damaged by floodwater with several thousand homes left without power. All of this thundery rain of course was falling on already saturated ground especially from the first week of June. These were some of the worst thunderstorms to hit Cork in recorded history.

I remember the June 2012 thunderstorms very well. Whilst I didn't hear any thunder where I am, the rain was very heavy and it was the second heaviest rainfall I have experienced after the morning of 18 November 2015.

Here's some videos from the June 2012 thunderstorms.

The lightning happens near the end of this video.







2009 - July 2009 was the wettest July on record for a large part of Ireland. On the 2nd, heavy thunderstorms brought exceptional falls of rain resulting in localised flooding. During the period from midnight to 09:00, thundery rain affected the east and northeast of Ireland, especially Dublin. Rainfall totals for the 9-hour period were around 40-50mm in parts of the city with 26.5mm being recorded within the hour 04:00 to 05:00 at Dublin Airport, the largest hourly rainfall total on record at Dublin Airport. During the afternoon and evening of the same day, another narrow band of thunderstorms or thundery rain affected Clare, Galway and Mayo bringing even heavier falls. Newport, Co. Mayo recorded up to 67mm with 41.6mm of this falling within one hour!

July 2009 had frequent thunderstorms with hail being observed at Cork Airport on the 29th. The 2nd July was the most notable of all the thunderstorms.

After a band of heavy rain passed through on the 20th October 2009, isolated thunderstorms were recorded in gusty southeasterly winds on the 21st including a daily rainfall of 28.5mm at Oak Park, Co. Carlow and 40.1mm at Mount Russell, Co. Limerick.





This picture is of cumulonimbus clouds over Dublin on 21st October 2009.



2008 - Like June 2012 and July 2009, August 2008 was a very wet month with absolute exceptional rainfalls and for some, the wettest August on record including at Phoenix Park whilst for others, not as wet as August 1986. On the 6th, Shannon Airport recorded an HOURLY rainfall of 38.4mm between 16:00 and 17:00 under a thunderstorm with hail, with almost 30mm of this being recorded within half an hour! This became Ireland's highest hourly rainfall total on record at a synoptic station for any month.

On the 9th, a cold front moved eastwards with a very unstable airmass immediately behind the front facilitating the development of thunderstorms in the east of Ireland following the frontal passage. Outbreaks of rain had affected the area earlier in the day from around 03:00 to 08:00 bringing totals of around 6-8mm. During the early afternoon, convective rain developed in the midlands. From approximately 13:30 onwards, a thunderstorm cell developed over west Offaly which then spread to north Kildare and eventually covered most of county Dublin and south Meath. Dublin Airport and Casement Aerodrome were reporting thunderstorms with further bursts of heavy rain continuing in the Greater Dublin Area until 22:30. Dublin Airport recorded a daily rainfall of 76.2mm under this thunderstorm, its second highest for any month and its wettest August day on record at that point (now second wettest August day and third wettest day after the 2nd August 2014). 68.3mm of this fell within a 5 hour period at the station. At Celbridge, Co. Kildare, 73.6mm of rainfall fell within the 5 hours whilst 77.8mm fell at Leixlip, Co. Kildare within the 5-hour period. Such rainfalls have return periods of between 150-240 years!

Here's some videos from the August 2008 thunderstorms.

This first one may seem familiar to Artane2002.







2007 - June 2007 was a very wet month in the east and south with it being Kilkenny's wettest June on record before the station closed in April 2008. Many of the showery days in the second half of the month were associated with thunderstorms.

Active fronts over Ireland on the 13th separated warm and humid air of tropical origin to the south and a cool arctic airstream to the north. As a result, some heavy thundery falls of rain occurred with a particular emphasis on the midlands. Mullingar measured an hourly rainfall between 14:00 and 15:00 on the 13th of 29mm with a return period of 50 years.

The 22nd brought heavy showers in from the west in a northerly wind direction. These showers, associated with thunderstorms, became unusually intense in parts of the east. Phoenix Park recorded a daily rainfall of 51.6mm on this day with 26mm of this falling within 90 minutes.

Here's a picture of Galtymore, Co. Tipperary on the 24th under a funnel cloud. Picture courtesy of Des Loughney.



2006 - Much of Summer 2006 was dry, settled and warm with a particularly warm start to June and mid-July period. Therefore, there wasn't much convection that took place but on the 9th/10th June, some localised thunderstorms took place out to the west and south. These weren't all that heavy however.

Here's a video from June 2006.



Not sure when this one was exactly in Summer 2006.



2005 - Heavy thunderstorms developed during the evening of the 29th June 2005 over many parts of Ireland giving some torrential falls locally and leading to flooding in parts of Munster and west Dublin. These showers were associated with a shallow depression which moved close to the southeast of Ireland during the day. Phoenix Park recorded a daily rainfall total of 41.2mm on this day according to Met Éireann's historical data but their June 2005 monthly weather summary states the station had 47mm in the hour of 17:35 to 18:35 on the day which included a 10-minute fall of 16.8mm. I am not sure which one is correct but nevertheless, both rainfalls are high. Cork Airport had recorded 13.5mm in thunderstorms.

On the 12th July, severe thunderstorms developed over the southern part of Ireland during the evening giving some torrential rainfalls and a tornado developed the same evening near Myshall, Co. Carlow. The 10th-12th brought hot and sunny weather everywhere over Ireland with temperatures getting as high as 30.3c on the 12th, you have to go back to July 1983 to see a higher temperature for July in Ireland up to that point. However, during the afternoon of the 12th, convective clouds developed producing heavy showers with thunderstorms in the southwest and southeast. Falls of between 20-25mm within a 3-hour period were recorded over Kerry, Cork and Tipperary.

Courtesy of Liam Clarke, this picture shows the tornado near Myshall, Co. Carlow on 12th July 2005.



2004 - The first part of July produced widespread thunderstorm activity over various parts of Ireland but there were no notable rainfalls.

August was a very warm month though not as warm as 2003 and unusually for such a warm Summer month, it was very wet for some. This was down to the fact that it was a showery month with regional variations. It was the wettest August in the east since 1986 at this time whilst the driest since 1995 in the northwest. Heavy showers were associated with numerous thunderstorms through August. On the 12th, Kilkenny recorded thundery rain with a daily rainfall of 32.2mm. Meanwhile, on the 18th, thunderstorms produced 32.8mm at Dublin Airport. Another notable thunderstorm occurred in Dublin on the evening of the 23rd resulting in flash or localised flooding, see the photo below (courtesy of Matthew Carrigan) of Clontarf, Co. Dublin on said evening.



2003 - Before the Summer really took off in August with warm, dry and sunny conditions, June/July were very warm but wet months. June contained some isolated thunderstorms but nothing really notable. However, on 20th July, slow moving thunderstorms brought localised flooding to parts of the west with Galway city being the worst affected. The station at NUIG measured a daily total of 39mm whilst in the east and even other parts of the northwest, there was little to no rain on that day. In general, July was a very humid and thundery month with easterlies being the prevalent wind direction dragging in a lot of cloud with these thundery showers. Another band of thunderstorms on the 29th July produced a tornado near Mullinavat, Co. Kilkenny causing some property damage.

Thunder was recorded during the heatwave of August 2003 but was mostly isolated with the exception of the 5th when thunderstorms were widespread over the east and south coasts and heavy causing disruption to power supplies.

2002 - The second week of July was very showery with hail and thunder being recorded in parts on the 10th. Funnel clouds or tornadoes not reaching ground level, were observed in parts of the south, west and northwest on the 9th.

2001 - A depression moved northwards from the Bay of Biscay on the 26th June introducing very warm and humid conditions with spells of thundery rain or showers. Some heavy thunderstorms affected the southeastern half of Ireland on this day which are indicated by the lightning symbol on the synoptic chart below for the 26th June 2001.

A line of thundery rain or showers associated with a frontal trough moved slowly eastwards over Ireland on the 13th July 2001. By afternoon, some heavy thunderstorms had developed over Munster and south Leinster but did not reach county Wexford until after nightfall. At Johnstown Castle, just south of Wexford town, rain commenced just before 23:00. Over the next two hours, a thunderstorm became almost stationary over the area giving continuous heavy rain at the station amounting to 65mm in the 2-hour period up to 01:00 on the 14th. This kind of event has a return period of more than 100 years. The 24-hour total at the station of 84.5mm was the second highest daily rainfall at the station in its 84-year history surpassed only by the fall of 111mm on August 3rd 1997. At nearby Clonroche, 63mm was recorded in the 24-hour period up to 09:00 on the 14th but Rosslare, less than 10 miles from Johnstown Castle, recorded a daily rainfall total of only 2.2mm.

The first part of August brought heavy and thundery rain to places leading to localised flooding. For example, on the afternoon of the 2nd, Cork Airport received 22mm in the space of 2 hours.



Radar at 23:45 on 13th July 2001.



2000 - Thunderstorms on the 30th June produced some very heavy falls in Mayo and Galway. Straide measured 39.6mm on this day whilst Crossmolina recorded 45mm in a 3-hour period on the evening of the same day.

The first week of July was dominated by very showery weather. Humid air circulating around an area of low pressure which moved slowly eastwards near the south coast brought a mixture of heavy, sometimes thundery, showers and sunny spells. Whilst some areas received over 20mm between the 1st and 5th, other areas were virtually dry. There were some particularly heavy thunderstorms in parts of the south and west on the 4th and 5th along with the midlands on the 3rd, when lightning damaged power lines and there was localised flooding. Near Westport, Co. Mayo, 22mm was recorded in an hour during the evening of the 4th. Nealstown, Co. Laois in the Slieve Bloom mountains recorded 63.6mm in a 2-hour thunderstorm on the 3rd. Near the end of July, a shallow depression became established over Ireland following a spell of settled weather. Showers became heavy and more widespread between the 27th-29th. Around 50mm was measured in the Clare/Limerick area during a thunderstorm on the 27th. A number of thunderstorms produced a daily total of 39mm at Shannon Airport on the same day.

Throughout August 2000, there were some localised heavy showers which were often accompanied by thunder and with some occasional torrential downpours. It was unusual just how frequent thunderstorm activity was during the month. Thunderstorms in the period 15th-20th around the middle of the month were accompanied by tornadoes. At Coolavin, Co. Sligo, a funnel cloud was observed on the afternoon of the 17th whilst around the same time, a waterspout or miniature tornado over water, was observed from an Air Corps helicopter over Clew Bay. A hailstorm over Skerries, Co. Dublin gave a covering of over 10cm of hail on the morning of the 20th giving the appearance of snowfall. The following day, a tornado at Toome Bridge, Co. Antrim, produced hailstones of 13mm diameter while at Aldergrove Airport near Belfast, there was a total of 7 days during the month with thunder - around its usual number for an entire year and the highest for any month at the station for exactly 50 years. Widespread thunderstorms were recorded on the 25th especially over the eastern half of Ireland giving falls of over 20mm to parts.

Skerries, Co. Dublin on 20th August 2000. Picture is taken from the August 2000 monthly weather bulletin thus why it's black and white.



Irish Independent article from August 24 2000 stating how good of a month August 2000 was for thunderstorms and hail.

https://www.independent.ie/irish-news/august-is-a-wicked-month-for-hailstorms-26112260.html

1999 - Much of August was mainly influenced by areas of low pressure giving spells of locally heavy rain. Some of this rain was accompanied by severe thunderstorm activity leading to reports of tornadoes from a number of locations during the month. The very warm, sunny weather of late July extended into the 1st of August in most places but the first of the month's frontal troughs was already approaching the west coast. These bands of thundery rain became slow moving over Ireland over the following days as the associated depression lay just off the southwest coast. Rain was particularly heavy in the south and east between the 4th and 6th where falls of over 50mm were measured during the period whilst a tornado struck the Sligo village of Ballisodare on the 6th. The weather around mid-month became showery as a depression lay to the north between the 14th-16th and some of the showers were very thundery in the fresh northwesterly airstream. Shower activity increased further as low pressure became centred over us on the 17th and 18th. Tornadoes were reported from Ballina and Portumna on the 17th whilst severe thunderstorms over southern Wexford on the 18th produced golfball sized hail and knocked out power supplies. Rosslare measured 27.5mm in a 2-hour period during the early afternoon of the 18th.

1998 - There was a very wet start to what was going to be one of the wettest Junes on record over the southern half of Ireland as bands of thundery rain or showers, associated with a depression crossing Munster, gave 2-day rainfalls of 20mm or more. A tornado struck near Dungarvan, Co. Waterford on the 1st. Two families staying at Ballyclamper Holiday Park were fortunate to escape without serious injury when the tornado destroyed the mobile homes in which they were staying. Dr. John Tyrell of University College Cork, who visited the area, reports that the tornado followed a southeast to northwest track for approximately 2.8km, commencing about 200m from the shoreline and had a width of 10m. The tornado developed during a 3 to 4-hour spell of heavy rain. Carriglea about 10km distant recorded 15mm of rain between 01:00 and 04:00 on the 1st. Some of the contents of the caravans were found over a kilometre away! On the 6th, a funnel cloud was observed at Lyreacrumpane, Co. Kerry as a frontal trough crossed the country giving some very heavy rain and squalls. That same afternoon, 18mm was recorded within 20 minutes at Birr. Birr remarkably enough faced a nine degree drop from 20c to 11c that afternoon within the space of 2 hours.

August wasn't a very thundery month but nevertheless, thundery downpours affected northern areas during the afternoon of the 11th. At Malin Head, flash flooding followed showers producing 15mm within the space of 2 hours, a maximum rate of 36mm/hr was recorded. Paddy Delaney, the head of the synoptic station at Malin Head at this time, reports that damage was widespread in the Malin Head area. Houses were flooded, stone walls ruptured and the tarmac surface removed from many stretches of road with the force of the water. Within a couple of hours, the only obvious evidence of anything unusual having happened was the large amounts of debris on the roads.

1997 - Heavy rain associated with thunder fell in western regions on the 10th and 12th July 1997. The rainfall recording at Bangor Erris measured 50mm of rain in 2 hours on the 12th whilst Belmullet's daily total of 29mm on the same day was its highest for July since 1987.

There were widespread thunderstorms on the 10th and 11th August with up to 34mm recorded at Valentia Observatory.

Here's a video of Baldoyle in August/September 1997 by highdef.



1996 - Thundery rain over Ireland on the 28th July brought some local downpours particularly in western counties. Worst affected was Boyle, Co. Roscommon where 83mm was recorded in an hour and a quarter by John McPherson, the observer at the rainfall station in Marian Road. This was one of the highest rainfall totals in a short period ever recorded in Ireland. Elsewhere on the 28th, torrential rain in the Erris Peninsula caused a landslide resulting in the deaths of 50 sheep while in east Galway, there were reports of a number of cattle killed by lightning during the evening of the 28th. A daily total of 63.4mm was recorded at Kingscourt, Co. Meath. These heavy rainfalls were in stark contrast to the dry spell from the 7th-20th July which had no measureable rainfall at all at Cork Airport.

1995 - A depression brought thunderstorms on the 16th July resulting in some heavy rainfalls to parts including Dublin Airport where 39.0mm was recorded on the day.

August 1995 began with a very warm easterly flow dragging in hot continental air and some sufficient instability for thundery showers to localised areas. This included 31.4mm falling at Birr on the 1st day of the month.

1994 - A depression moved slowly northeastwards on the 24th June bringing frequent thunderstorms, especially in the north and east of the country. On this day, Clones recorded 38.5mm.

1992 - June was a dry month generally and indeed much of the rain that did fall can be accounted for a few heavy, often thundery, rainfalls on particular days. 100mm of the monthly rainfall total for June 1992 of 125mm at Cloosh in Connemara was recorded on the 29th. Similarily, 37mm was recorded during June at Dublin Airport and 26mm of this fell on the 2nd (over 20mm of that within an hour) whilst a drought occurred at the station from the 6th to the 29th (24 days).

1986 - June brought a very thundery start to the Summer of 1986 and we would have to wait 'til August 2000 to see a month as thundery as such. The first half of the month was dominated by westerly winds leading to generally cool and unsettled conditions but high pressure developed to the east around the middle of the month and low pressure that affected us tended to come from Europe than the Atlantic. Therefore, the temperatures rose and brought quite a lot of thunderstorm activity. The most notable of the thunderstorms occurred on the 27th and 28th causing widespread damage and destruction. In Dublin, about a dozen houses were struck by lightning and at least one was gutted by the resulting fire. Power supplies, transport and communications were disrupted and computers, cable television and other electrical equipment knocked out. 26.5mm fell at Birr on the 28th.

Here's RTÉ Archive coverage on June 1986 thunderstorms for 27th/28th.

https://www.rte.ie/archives/collections/news/21219093-thunder-and-lightning-storm-damage/

1985 - For this one, I'll leave you with just the RTÉ Archive coverage on it for the July 25th/26th 1985 thunderstorm for now (I will do a more detailed post on it in future). See Gaoth Laidir's analysis on it here:

https://www.boards.ie/vbulletin/showpost.php?p=106115073&postcount=195

http://www.rte.ie/archives/collections/news/21200391-freak-storm-causes-damage

1983 - A hot spell in July that led to water shortages was followed by a severe thunderstorm to parts of the southeast with Kilkenny in particular. On the morning of the 17th July, this thunderstorm moved up the Nore valley. Nearly 1 inch of rain was recorded within 15 hours at the Kilkenny synoptic station on the day and this remains one of the highest on record for that space of time. The thunderstorm was quite slow moving, local to the Kilkenny area and not accompanied by hail. The ground was parched and hard beforehand and as the rain bucketed down it behaved like concrete, with little absorption. Just when things were beginning to reach crisis levels and cause untold damage, the rain subsided and widespread flash flooding was avoided. Here are the accumulative rainfall totals (mm) for Kilkenny on 17th July 1983 with the 66.4mm daily rainfall making it Kilkenny's wettest day on record in what was otherwise a very dry July!

15 mins|30 mins|1 hour|2 hours|6 hours|12 hours|24 hours
23.5|31.6|37.9|56.7|65.7|66.4|66.4


If you'd like me to do a separate post on any of the above (again if possible), just ask. There's plenty more thunderstorms that have occurred in Ireland of course but that's the general history back to 1983.

All data comes from Met Éireann.

The last quarter (October to December) of 1954 was very wet with the east of Ireland getting particularly affected badly. In some parts of Meath, their average rainfall was up to 170% of the average for the period. Dublin Airport recorded 100mm or more in each of the months with a total of 335.1mm for the period. That's almost more than what Glasnevin, Co. Dublin recorded throughout the whole year of 1887 which had 356.6mm at the station. Late November and early December 1954 brought an especially wet and windy spell of weather. There were a number of ships sunk or run aground off the Irish coast. These were described in newspaper reports as "mountainous seas".

Flooding was widespread in many parts before a band of heavy rain moved eastwards late on December 6th, clearing for a while on the 7th before another band of persistent and heavy rain became established in all areas on the 8th. Rain was particularly heavy over eastern counties with more than 80mm falling between the 6th and 8th December. Dublin Airport recorded a daily rainfall of 49.0mm on the 8th, its wettest December day on record to this day.

Early on the 9th, the swollen river Tolka undermined the foundations of the railway bridge across the river at Fairview. The collapsed bridge then formed a barrier across the river causing water to flow out across a very wide area; approximately 1,500 houses accommodating 2,000 families were affected by the flood waters and several hundred people were forced to evacuate their homes. There was extensive flooding elsewhere across the city, particularly in the Kilmainham area along the river Camac whilst the Shannon reached its highest level since 1925 and many thousands of acres of farmland were inundated. There were reports of widespread power outages on the 8th with further disruption caused by heavy falls of snow in parts of the midlands and northwest! Essentially, Dublin was like Venice.

Data comes from Met Éireann.

Pictures of the North Strand, Dublin in December 1954.













https://www.irishtimes.com/opinion/an-irishman-s-diary-1.781443

On November 5th/6th 2000, the east of Ireland suffered their wettest November days since 1982. Rain began early on the 5th over Kerry as a depression of 972hPa approached the southwest coast. The depression moved eastwards over Munster during the day deepening to 969hPa over southern England by 12:00 on the 6th. By 09:00 on the 5th, heavy rain had spread into most eastern, southern and midland areas. It was continuous near the east and southeast coast until the afternoon of the 6th. There was considerable flooding in the east and southeast following the rainfall with widespread disruption of transport. Flood damage to property is estimated at £40 million.

In addition to the heavy rain, there were easterly or northeasterly gale to storm force winds near southern and southeastern coasts during the same period. Rain continued to linger in eastern and northeastern regions on the 7th.

Some daily rainfalls (mm) for the period.

Station|County|Rainfall total|Date
Casement Aerodrome|Dublin|55.5|5th
Casement Aerodrome|Dublin|36.1|6th
Dublin Airport|Dublin|41.2|5th
Dublin Airport|Dublin|32.6|6th
Glenasmole|Dublin|137.2|5th
Leixlip|Dublin|90.8|5th
Phoenix Park|Dublin|76.2|5th
Celbridge|Kildare|56.0|5th
Naas C.B.S|Kildare|51.4|5th
Ratoath|Meath|52.0|5th
Warrenstown|Meath|62.4|5th
Glenmacnass|Wicklow|142.0|5th
M.Sally Gap|Wicklow|148.7|5th
M.Sally Gap|Wicklow|37.4|6th
Roundwood|Wicklow|94.0|5th
Arklow|Wicklow|77.7|5th
Cappoquin|Waterford|97.8|5th
Clonmel|Tipperary|70.1|5th


All of this was falling onto already very saturated ground from what had been a very wet start to the Autumn season with one of the wettest Octobers on record and whilst it was not as wet as September 1999, September 2000 was also quite a wet month. Autumn 2000 remains the wettest Autumn on record to this day with so many major flooding events taking place, this one on November 5th/6th was one of them. Funny fact is that I was born nearly exactly a week after this flooding event took place.

Data comes from Met Éireann.

Very similar chart to that of December 8th 1954.





Here's an RTÉ Archive video on the event.

https://www.rte.ie/archives/2015/1104/739593-flooding-in-ireland/





The BBC even mention us here.



Courtesy of Steve Humphreys, Lucan, Co. Dublin in November 2000.



https://www.irishtimes.com/sport/garden-of-earthly-delights-where-floods-are-par-for-the-course-1.320461

This post is for Clonmel1000 for 9 June 1993.

This day was relatively warm for most places with temperatures in the high teens and low 20s for some. The maximum reached on the day was 22c though I cannot find the station that recorded this. Places out to the west though only got between 14-16c including a maxima of just 14.5c at Belmullet, Co. Mayo.

A front lied over the west of Ireland bringing some rain here and getting heavy at times. Meanwhile, a thundery trough pushed northwards from the south at the same time which added energy to the front out west. The combination of the two produced a lot of rain for some.

Here's some rainfall totals from the day

Station|Rainfall total (mm)
Clonmel (Ballingarane)|10.8
Cork Airport|27.0
Fermoy (Moore Park)|40.2
Roche's Point|17.8
Shannon Airport|13.8






The precipitation charts from the CFS reanalysis archive don't really show the intensity of the rainfall.



Data comes from Met Éireann.



However, this was nothing like what was going to happen 2 days later in the east of the country on 11 June 1993. That's an event for a different day though.

Going to talk about something recent again today and it's the remnants of ex-hurricane Gert from 20th-22nd August 2017.

First, let me give some background information on hurricane Gert. Gert was a category 2 hurricane that brought heavy surf and rip currents to the eastern coasts of the US. It originated from a tropical wave off the coast of Africa on August 3rd 2017 but did not become a tropical depression until August 12th near the Bahamas. It became the seventh tropical storm of the 2017 hurricane season and was named Gert a few hours later on the 12th. Dry air hindered intensification of Gert until the 14th when the storm resumed strengthening whilst moving northwards. The storm reached its peak intensity on the 16th and became a category 2 hurricane on the Saffir-Simpson scale. Thereafter, increasing vertical wind shear and cooler sea surface temperatures caused the hurricane to weaken and transition into an extratropical cyclone on the 17th. The remnants of Gert dissipated late on the 18th as they merged with another extratropical cyclone over the Atlantic. This would later bring heavy rainfalls and strong winds to both the UK and Ireland.

Met Éireann issued yellow status warnings for the entire of Ireland expecting heavy showers and localised flooding. Severe floods occurred in Northern Ireland with floodwaters reaching 1.5m. More than 100 people were rescued after being trapped in their cars or houses overnight.

Some rainfall totals from 21st August 2017.

Station|Rainfall total (mm)
Mace Head|35.3
Newport|31.4
Belmullet|30.0
Claremorris|24.2
Gurteen|22.0
Knock Airport|21.4
Athenry|15.4
Mt. Dillon|14.6
Finner Camp|14.3
Mullingar|13.5


Some rainfall totals from 22nd August 2017.

Station|Rainfall total (mm)
Carndonagh|81.4*
Malin Head|77.2
Lough Fea|61.0
Finner Camp|31.8
Mt. Dillon|26.4
Markree Castle|23.8
Ballyhaise|16.7


*This recording from Carndonagh was from 09:00 on the 22nd to 09:00 on the 23rd.

According to Gerry Fleming, around 63mm of Malin Head's total there fell in the space of 6 hours and 32mm of it in two hours between 19:00 to 21:00 on the 22nd. It was one of the wettest days on record at Malin Head.

Data comes from Met Éireann.







Northern Ireland flood on 23rd August 2017.



https://www.irishnews.com/news/northernirelandnews/2017/08/23/news/torrential-rain-causes-flood-damage-1118086/

Ok so, the answer was Summer 1950 to the post above (I made a mistake by saying it ended in 8). This was indeed Ireland's wettest Summer on record until 2009 took that title. Valentia Observatory had a seasonal rainfall total of 454.4mm, 2009 in comparison at this station had 619.7mm of rain. Looking at these figures, 1950 pales in comparison to 2009 as 2009 recorded nearly 200mm more than 1950 at Valentia Observatory. At Dublin Airport, Summer 1958 was far wetter than 1950 though. The reason why it wasn't as wet (though still wetter than average) in the east lies in the reanalysis below, the trough is just out to the west than over the country and somewhat of a southwesterly component to the wind direction.



1950 and 2009 share some similarities. June in both years were very warm months whilst in 1950, it was quite a dry month. At Valentia Observatory, this was the driest June since 1940 with a rainfall total of 64.9mm following a very dry May too. 1950 was the perfect definition of a front loaded Summer though as it went completely down hill thereafter with July being one of the wettest on record and whilst August wasn't a record breaker, it was still very wet. Dublin Airport recorded 145.8mm of rain in August 1950; this up to 2017 is the station's 5th wettest August on record. This wet weather continued into September with the wettest September on record at many stations until 1999. In contrast, September 2009 was a very anticyclonic month with a drought being recorded in places.

I don't have IMT figures for 1950 but the CETs for each of the months were 16.2c, 15.9c and 15.6c for June, July and August respectively. Up to 2017, June 1950 was the equal 15th warmest June on record for the CET. July and August's CET values were very average for their time - whilst relatively cool nowadays.

June 1950 featured a very early warm spell with heatwave-type conditions for parts of the UK and the most significant early June warm spell since 1947. It wasn't a definitive heatwave because it lasted for 2 days. 33.3c was recorded at London on June 6th 1950 whilst even Glasgow got up to 31.3c on June 7th. Dublin Airport reached 25.9c on the 6th whilst Shannon Airport got up to 27.3c on the same day.

Other than the Valentia Observatory seasonal total, 1950 doesn't really stand out in the record books unlike let's say Summers 2007-2009. Despite being so wet for some though, it was a sunny Summer and in the east whilst not as sunny as 1949, it was a very sunny season. So strange!

Valentia Observatory's daily rainfall for Summer 1950.



Data comes from Met Éireann and the UK Met Office.

A very typical chart on 9th July 1950.

echat wrote: »

Why not May to July summer, makes more sense for daylight and maybe even rainfall.

Meteorologically, Summer comprises of June to August.

It's not about daylight at all plus May is drier for the majority of places than any of the "Summer" months on average. It's the warmest months of the year on average that make this the way it is.

It looks like the June 13th quirk is safe for another year. Remember that this is the only date of the meteorological Summer season that has failed to reach 30c in the UK. The date record is 28.3C set in 1896, 1948 and 1994. Many days of May, September and even some October/April days have recorded higher maximum temps in history than June 13th. Most recent example being April 19th 2018 with 29.1c.

echat wrote: »

Any reason why air temperature in August is warmer than in May if the latter has more sunshine hours? Assuming a gradual heat build-up is the reason then presumably the hottest part of the year at the coast tends to happen later than the hottest part of the year inland?

Yes, it's the fact of building up the heat. In May, both the land and sea are still warming up from Winter and Spring from any cold spells or snaps compared to August when it has all heated up to its highest extent for the year before it starts to cool down again when temperatures go below average during the Autumn. The same is said to Europe where the continent is at its warmest around high Summer time and when we get our warmth, it tends to come from southerlies, southeasterlies or easterly winds with air from Europe. As a result of things like this, September can be warmer than May the majority of the time too.

How May is the sunniest month of the year on average (not always though) in Ireland is explained in detail by M.T. Cranium here: https://www.boards.ie/vbulletin/showthread.php?p=103600724

There's a reason why the infamous phrase: "Return of the westerlies" (from the second half of June onwards) exists .

30c has occurred in August a few times in Ireland but has never occurred in May before - as far as Irish records go back that is, could have lots and lots of years ago (I'm talking centuries back) but that's the problem with data. Even if we found somewhere that reported 30c at some point in a historical May in Ireland, its reliability is questionable.